Question

Chromium is most commonly mined in the form of chromite, which has the chemical formula fecr2o4. calculate the percent by mass of each element in chromite, and give your answers to four significant digits.

Answer 1

Fe atomic mass = 55.86 * 1 = 55.86 Cr atomic mass = 52 *2 = 104 O atomic mass = 16 * 4 = 64 Total molecular mass = 223.86 Percent by mass Fe = (55.86/223.86)*100 = 24.95% Percent by mass Cr = 46.45% Percent by mass O = 28.59%

Answer 2

The mass of each elements in chromite is as below

Fe =24.9 %

Cr =46.5%

O = 28.6%

calculation

percent mass = atomic mass of element / atomic mass of FeCr2O4 x 100

from periodic table the atomic mass for Fe = 55.85 g/mol,

Cr =52 g/mol since they are two atoms in FeCr2O4 = 2 x 52 = 104 g/mol

for O = 16 since they are two atoms in FeCr2O4 = 16 x4 = 64 g/mol

Atomic mass for FeCr2O4 is = 55.85 +104+ 64 = 223.85 g/mol

Percent mass for Fe =55.85 /223.85 x100 = 24.9 %

for Cr = 104 / 223.85 x 100 = 46.5%

For 0 = 64/223.85 x 100 = 28.6%